Air conditioning (A/C) systems provide cool air that is circulated in buildings. A/C systems are thermo-dynamic devices with a cold side and a hot side. Refrigerant is circulated in the A/C system and undergoes gas-liquid and liquid-gas state changes that enable cooling of air. The hot side of the A/C system induces a state change in the refrigerant from a gas to a liquid state by transferring heat from the refrigerant to atmosphere. The cold side of the A/C system induces a state change in the refrigerant from a liquid to a gas state by transferring heat from ambient air within the building to the refrigerant. The heat transfer from the ambient air to the refrigerant cools the ambient air in the building.
The cold side of the A/C system is located within the building to cool ambient air within the building. The cooled air is circulated through the building by an air handler, such as a furnace and a blower. The hot side of the A/C system is located external to the building and includes a condensing unit.
The condensing unit typically includes a compressor, a condensing coil, a fan blade, and an electric motor. The compressor compresses and moves the refrigerant in the condensing coil. The electric motor rotates the fan blade to induce air flow through the condensing unit. The air flow improves heat transfer of the refrigerant in the condensing coil and improves condenser efficiency.
Typically, the electric motor of the condensing unit is a permanent split capacitor (PSC) motor that includes an inner rotor that rotates within an outer stator. The PSC motor also includes a shell and two stationary end shields. The PSC motor is mounted in a shaft downward position from the top of a housing containing the condensing unit. The electric motor rotates the fan to induce upward air flow through the condensing unit.
The housing for the condensing unit typically has a defined height. Due to their construction, conventional PSC motors are longer in an axial direction than desired. When the motor is mounted in the shaft downward position, the fan blades are located a significant distance from the top of the condensing coil assembly. In other words, a top portion of the condensing coil lies above the fan. The top portion of the condensing coil that is at or above the height of the fan blade does not receive air flow and has a lower heat transfer efficiency. In some condensing units, the electric motor is mounted in a shaft upward position to improve the condensing unit efficiency. This approach increases the cost of both the motor and the condensing unit.
Performance attributes of AC systems can be improved in several areas. AC systems generate undesirable acoustic noise during operation due to the operation of the fan and/or the compressor. Some of the acoustic noise that is created by the fan can be attributed to the electric motor. In other words, reducing acoustic noise of the PSC motors would decrease the acoustic noise of the AC system.
AC systems also consume a relatively high amount of power due to the operation of the electric motor and/or compressor. Reducing the “on” time of the fan by increasing the efficiency of the condensing unit would be desirable. Furthermore, reducing the power that is dissipated by the electric motor would also be desirable.